In recent years, for a light source of an image display device that is one of an optical application device and a head lamp of a vehicle, an LED light source and a laser light source having superior power consumption efficiency and a long product life are used. Particularly, the LED light source has restrictions of the operating environment (temperature and humidity) less than the laser light source and a stable operation and becomes the mainstream.
An LED having high output as a light source of an image display device, generally, is a surface emission light source and cannot collect light into an image display element that is a light receiving unit with high efficiency based on a conservation law of etendue (Etendue=emission area of light source×divergence angle) in a case where the LED is used for a lighting optical system. For this reason, a light source system having a new configuration has been proposed in which a laser light source having a small area of a light emission portion and superior straightness as a primary light source emits laser to a fluorescent substance for excitation so as to acquire light (see Patent Documents 1 and 2).
On the other hand, in recent automotive lightings, a configuration in which an LED is used as a light source, and light distribution characteristics are controlled using an optical lens formed using plastic and a reflector (reflecting mirror) becomes the mainstream (see Patent Document 3).